A surfactant
is a substance that can greatly reduce the surface tension of water when
used in low concentrations (37, 39). They are soluble surface-active agents
comprised of a hydrophobic portion, usually a long alkyl chain that is
attached to hydrophilic functional groups (38, 39). The hydrophilic end of
the surfactant is strongly attracted to the water molecules, and the force of
attraction between the hydrophobe and water is only slight. As a result, the
surfactant molecules align themselves at the surface so that
the hydrophilic end is towards the water, and the hydrophobe is squeezed away
from the water. (37, 39). A surfactant can be classified by the presence of
formally charged groups in its head. A nonionic surfactant has no charge
groups in its head. The head of an ionic surfactant carries a net charge. If
the charge is negative, the surfactant is more specifically called anionic;
if the charge is positive, it is called cationic (39). Often a combination
of surfactants is used to produce good grease cutting capability, soil
suspension, and mildness in water of varying degrees of hardness (37,38).

The shampoo Fructis is composed mainly of
Sodium Lauryl Sulfate or SLS. SLS is a wetting agent, that allows the
shampoo to spread easier and penetrate more profoundly. It is a cheap
ingredient and mixed with Sodium Stearate, usually composes approximately
fifty percent of a shampoo’s ingredients. About forty percent is water and
the other 10 percent are preservatives, fragrance, and color (33, 34).

The laundry detergent, Ariel, is composed
mainly of Alkyl Ethoxylate Sulfate or AES. It is a relatively strong
non-ionic emulsifier that has high water solubility (35, 36). It also
reduces the surface tension of water thus allowing for the better
elimination of greasy stains.

The chilean dishwashing liquid, Quix, is
composed mainly of Alkyl Polyglycoside and N,N'-bis(3-aminopropyl) Propane-1,3-Diamine.
The first chemical is responsible for destroying bacteria when in contact
with water, while the latter functions as a surfactant to remove grease
stains and reduce water tension.